Edward victor espenhahn



UNITED- STATES PATENT OFFICE.

EDWARD VICTOR ESPENHAHN, 0F BRIGHTON, VICTORIA, AUSTRALIA.

TREATMENT OF GASES OBTAINED FROM COAL AND OTHER GAIRBONAGE-OUS FUEL.

No Drawing.

To all whom it may concern:

Be it known that I, Eowann Vroron Es- PENHAHN, a subject of the King of Great Britain, residing at 1 William Street, Brighton, in the State of Victoria, Commonwealth of Australia, have invented certain new and 'useful Improvements in the Treatment of Gases Obtained from Coal and other Carbonaceous Fuel, of which the following is a specification.

This invention relates to certain improvements -in the treatment of gases obtained from coal and other carbonaceous fuel and refers more especially to the treatment of heating and illuminating gases containing cyanogen hearing compounds obtained from the distillation of coal in ordinary" gas works or from the manufacture of 'coke in coke ovens.

This invention ,is also applicable to other gases which contain cyanogen bearing compounds (such as producer gas and blast furnace gases). D

The object of this invention is to provide means for the recovery of cyanogen bearing compounds from such gases and also other lay-products such as sulfate of ammonia. A further object of this invention is to provide a method of treatment which is c clic in operation whereby the products 0 subsequent operations are reusable in the treatment of fresh supplies of crude gases.

Hitherto man attempts have been made to extract solub e ferro cyanide from coal and coke oven gases but up tothe present these attempts have been more or less unsuccessful owing to the formation of insoluble compounds. These failures have been experienced both when the ammonia has been previously removed and when ammonia-1s present. In cases where ammonia has not been removed its resence, by slightly increasin the alkalinity, at first assists the absorption of the cyanogen-bearing substances, but after a certain point has been reached insoluble ferro-cyanids have been formed.

I have discovered that if the absorption of the cyano on hearing substances is carried out at refittively high temperatures (say from 40 to 90 0. approximately the dew point) or at the temperature ordinarily employed for direct recovery and if the solution is maintained at a relativelyhigh state of concentration approximately the oint of saturation the formation of insolub e ferro- Speciflcatlon of Letters Patent.

Patented Sept.9, 1919.

cyanids is avoided irrespective of the presence of ammonia even if present in comparatively large proportions.

I accomplish the objects of this invention by providing a method of treatment which comprises submitting the gases at a relatively high temperature to treatment with a concentrated alkaline solution (such as sodium carbonate) containing sodium ferrousferro-cyanid in suspension until the solution becomes charged with. sodium ferrocyanids; than allowing the solution to cool for the crystallization of the sodium ferrocyanid, then treating the sodium ferro cyanid thus obtained with an acid (such as sulfuric acid) for the formation of hydrocyanic acid (and subsequently alkaline cyanids) and sodium ferrousferro-cyanid which,latter may be advantageously used with sodium carbonate for treating the crude ases inthe first operation. The gases after tie removal of the cyanogen bearing compounds and containing ammonia and sulfureted hydrogen may be passed through a solution of ferrous sulfate for the formation of ferrous sulfid for use in producing the sodium ferrous-ferro-cyanid.

This invention is applicable" to the treatment of gases either by the direct or the semi-direct methods for the recovery of ammonia and may be applied either before or after the removal of'the ammonia.

.By way of example I will describe the treatment according to this invention of ordinary coke oven ases obtained from the destructive distillation of coal in which the recovery of the cyanogen bearing compounds is effected before the removal of the ammonia. The gases are firsttreated in the ordinary centrifugal or other washers for are led into washers preferably of the centrifugaltype at a temperature of approximate y the dew point 0 the gases (1'. .e. from 40 C. to 90 C.) and while still at that temperature are brought into intimate contact with a washing liquor, which consists of a concentrated solution of sodium carbonate in which sodium ferrous-ferro-cyanid is held in suspension. The production of this sodium ferrous-ferro-cyanid may be effected in the first instance by submitting the gases to washing with a solution of sodium carbonatein which ferrous sulfid is held in suspension formin sodiumferro-cyanid which is decomposed y sulfuric acid to form sothe removal of tar fog and without coolingdium ferrous-ferro-cyanid. The extent of concentration of this solution of sodium carbonate is obtained b adding the requisite quantity of such reagent as calculated to obtain subsequently a concentrated solution of sodium carbonate and sodium ferro-cyanid. I have found in practice that a solution made up by dissolving four lbs. of dehydrated sodium carbonate per gallon of water well answers the purpose. In practice preferably two or more se a'rate tanks or containers of this washing iquor are maintained so that as one is being withdrawn the other is in circulation. The gases are caused to pass through the said liquor while the same is mainw ued in a constant state of agitation by the centrifugal action of the washer. The temperature is maintained at or about the dew point of the gases by the admission of steam or other heating medium as may be found necessary. In practice sodium fcrrous-ferro-cyanid may be added from time to time to maintain the reaction which is in accordance with the following equation Na FeFe CN +H s-l-Na CO z Na Fe (ON) +FeS+CO +H O When the liquor contained in one storage tank has become sufficiently charged with sodium ferro-cyanid the liquor contained in the second tank is by-passed into the first gas washer and the first mentioned liquor is withdrawn and the sludge separated from the clear liquor such as by filter pressing or the like. The clear liquor is then allowed to cool when pure crystals of sodium ferrocyanid are formed. The clear liquor is returned to the washing storage tank after having been renewed by the addition of sodium carbonate and sodium ferrous-ferrocyanid. The sodium-ferro-cyanid obtained as above is treated with sulfuric acid for the formation of hydro'cyanic acid (and subseuentl alkaline cyanids) inaccordance with t e fo lowing equation FeS+2Na CO +6HCN:

Na Fe GN) -l--H,,S-l'-2H O-}-2C() The gases after theremoval of the cyanogen bearing compounds are caused to travel to ammonia saturators in which they are subjected to the action of sulfuric acid in the ordinary way for the formation of ammonium sulfate. Or alternatively such gases or a portion of such gases may be assed through a solution of ferrous sulfate or the formation of ammonium sulfate free from cyanogen bearing compounds and ferrous sulfid in accordance with the following equa tion:-

FeS0 +H S+2NH urn 2S04+F6S The ferrous sulfid obtained as above may be used in conjunction with sodium carbonate for washing the crude gases as above described for the formation of sodium ferrocyanid.

Another example of this invention consists of its application to the treatment of gases in which the cyanogen bearing compounds are recovered after the removal of the ammonia. In this case the gases are treated in the ordinary way for the removal of the tar fog and ammonia and are then subjected to a washing treatment at a rela tively high temperature (approximately the dew point of the gases) with a concentrated solution of sodium carbonate in which sodium ferrous-fcrro-cyanid is held in suspension. The same reactions take place as described above producing sodium ferro-cyanid in solution. The liquors are treated for the separation of the sludge and the clear solution is allowed to cool for the precipitation of crystals of pure sodium ferro-cyanid. This sodium ferro-cyanid is treated with sulfuric acid for the formation of hydrocyanic acid and subsequently alkaline cyanids while the sodium ferrous ferro-cyanid formed is used with the concentrated solution of sodium carbonate for treating fresh supplies of the gases for the formation of sodium ferro-cyanid as previously described.

A certain portion of the gases before being led into the ammonia saturators is b passed into another washer where the sald gases containing ammonia and sulfureted hydrogen are caused to ass through a solution of ferrous sulfate 'or the formation of ammonium sulfate and ferrous sulfid. This ferrous sulfid may be used as above described for treating fresh gases with a concentrated solution of sodium carbonate for the formation of sodium ferro-cyanid.

claim: a

1. In the treatment of gases obtained by the heat-treatment of coal and other car bonaceous fuel, submitting the said gases at a relatively high temperature correspondin approximately to the dew point of the sai gases, to a treatment with a concentrated solution of an alkali containing sodium ferrous ferro-cyanid in suspension.

2. The method of treating gases obtained by the heat-treatment of coal and other carbonaceous fuel, which comprises separating the tar fog; then submitting the said aces to a washing operation at a relatively i h tem )erature corresponding approximate y to t e dew point of the said gases, with a concentrated solution of sodium carbonate containing sodium ferrous ferro-cyanid in suspension until the solution becomes charged with sodium ferro-cyanid, ailowiug the solution to cool until the sodium fcrro-cyanid crystallizes out' treating the said sodium ferro-cyanid with-acid for the formation of hydrocyanic acid and sodium ferrous ferro-c anid; and washing a further amount 0 the said gases with a concentrated solution of sodium carbonate containing this sodium ferrous ferro-cyanid.

3. Method of treating gases obtained from coal and other carbonaceous fuel consisting of first treating the said gases for the removal of the tar fog; treating such gases for the absorption of ammonia; submitting the gases to treatment with a concentrated solution of sodium carbonate containing sodium ferrous ferro-cyanid in suspension until the solution becomes charged with sodium ferro-cyanid; allowing the said solution to cool until the sodium ferro-cyanid crystallizes out, treating the said sodium ferro-cyanid with acid for the formation of hydrocyanic acid and sodium ferrous ferro-cyanid; and utilizing such sodium'ferrous ferro-cyanid for treating fresh gases in conjunction with a concentrated solution of sodium carbonate.

4. In the treatment of coal gas, coke oven gas and the like, the process of recovering cyanogen compounds contained therein, which comprises passing such gas, while warm, into contact with a concentrated solution of an alkali containing an iron compound capable of uniting with the said cyanogen compounds.

5. In the treatment of coal gas, coke oven gas and the like, the process of recovering cyanogen compounds contained therein, which comprises passing such gas, while warm, into contact with a concentrated solution of an alkali containing an iron compound capable of uniting with the said cyanogen compounds, and thereafter removing a cyanogen-alkali-iron compound from the liquor and regenerating therefrom an iron compound suitable for use in the first part of the process.

6. The step of treating cyanogen-containing gas with a concentrated solution of soda containing in suspension an iron compound capable of reacting with the soda and the cyanogen of the gas to form sodium ferrocyanid, said treatment being effected while said gas is maintained at approximately the dew point.

7. In the treatment of gases produced in the heat-treatment of coal, which gases contain cyanogen, the step of washing such gases with a liquor comprising sodium ferrous ferro-cyanid, suspended in a concentrated soda solution, while at about the dew point pf the gases.

In testimony whereof I have signed my name to this specification in the presence of two subscribing Witnesses.

EDWARD VICTOR ESPENHAHN.

\Vitnesses:

J. L. CULLEN, LUCY M. GREEN. 

